linux-kernel - Re: [PATCH RFC 03/24] vfs: add try_break_deleg calls for parents to vfs

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Date: Sat, 16 Mar 2024 23:57:17 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Jeff Layton <jlayton@...nel.org>
Cc: Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	Chuck Lever <chuck.lever@...cle.com>,
	Alexander Aring <alex.aring@...il.com>,
	Trond Myklebust <trond.myklebust@...merspace.com>,
	Anna Schumaker <anna@...nel.org>, Steve French <sfrench@...ba.org>,
	Paulo Alcantara <pc@...guebit.com>,
	Ronnie Sahlberg <ronniesahlberg@...il.com>,
	Shyam Prasad N <sprasad@...rosoft.com>, Tom Talpey <tom@...pey.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	David Howells <dhowells@...hat.com>, Tyler Hicks <code@...icks.com>,
	Neil Brown <neilb@...e.de>, Olga Kornievskaia <kolga@...app.com>,
	Dai Ngo <Dai.Ngo@...cle.com>, Miklos Szeredi <miklos@...redi.hu>,
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	Namjae Jeon <linkinjeon@...nel.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
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	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-nfs@...r.kernel.org, linux-cifs@...r.kernel.org,
	samba-technical@...ts.samba.org, netfs@...ts.linux.dev,
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	netdev@...r.kernel.org
Subject: Re: [PATCH RFC 03/24] vfs: add try_break_deleg calls for parents to
 vfs_{link,rename,unlink}

On Fri, Mar 15, 2024 at 12:52:54PM -0400, Jeff Layton wrote:
> @@ -4603,9 +4606,12 @@ int vfs_link(struct dentry *old_dentry, struct mnt_idmap *idmap,
>  	else if (max_links && inode->i_nlink >= max_links)
>  		error = -EMLINK;
>  	else {
> -		error = try_break_deleg(inode, delegated_inode);
> -		if (!error)
> -			error = dir->i_op->link(old_dentry, dir, new_dentry);
> +		error = try_break_deleg(dir, delegated_inode);
> +		if (!error) {
> +			error = try_break_deleg(inode, delegated_inode);
> +			if (!error)
> +				error = dir->i_op->link(old_dentry, dir, new_dentry);
> +		}

A minor nit: that might be easier to follow as
		error = try_break_deleg(dir, delegated_inode);
		if (!error)
			error = try_break_deleg(inode, delegated_inode);
		if (!error)
			error = dir->i_op->link(old_dentry, dir, new_dentry);

and let the compiler deal with optimizing it - any C compiler is going to be
able to figure out that one out.  vfs_link() is a mix of those styles anyway -
we have
        if (!error && (inode->i_state & I_LINKABLE)) {
                spin_lock(&inode->i_lock);
                inode->i_state &= ~I_LINKABLE;
                spin_unlock(&inode->i_lock);
        }
immediately afterwards; might as well make that consistent, especially since
you are getting more shallow nesting that way.